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Fastener enterprises how to choose the annealing furnace

In the process of the production of fasteners, in order to facilitateCold heading moldingGenerally it will be drawn and Rod ball annealing process. The ball annealing quality is good or bad, will directly affect the quality of the final product is good or bad. Then, as a fastener manufacturers, how to choose a suitable annealing furnace it?

First, we need to understand the purpose of spheroidizing:

1, to improve the mechanical properties and reduce the material hard, strength and improve cold workability;

2, the workpiece to a lower energy forging forming, easy cutting;

3, to reduce die wear and tear;

Avoid workpiece burst, distorted.

Secondly, we need to understand the relationship between performance and cold heading quality ball between the

1, the deformation resistance:

And the hardness and tensile strength of the material related.

Hardness Deformation resistance
The lower the lower the

2, the deformation energy:

And the microstructure of the material related, such as full annealing, normalizing tissue deformation can be worse than the ball of the organization. On the ball in terms of the group, when cementite (Fe3C) of the spheroidal ratio is higher, the more good deformability; and cementite (Fe3C) into fine particulate uniformly dispersed in the ferrite, which can deform the most good.

Third, we need to understand a few indicators After a Rod ball annealing usually concern:

1, surface oxidation

2, the surface decarbonization;

3, hardness and hardness uniformity;

4, the rate of the ball

5, microstructure

Next, we analyze the impact these indicators one by one fastener production:

Surface oxidation and decarbonization:

Oxidation of the material surface, can cause loss of material (allowance amplification), so production costs (material loss, prolonged rust). Surface decarbonization serious cause of degradation products, the strength, and even produce waste.

The key to solving the surface oxidation and decarbonization of the precise control of the furnace atmosphere! Only precise control of furnace atmosphere oxygen potential value in order to achieve a non-oxidizing micro and decarbonization; if simply passed through some of the gas can not be accurately controlled, also help solve the problem of surface oxidation and decarbonization.

GB surface decarbonization requirements for the 15 ‰ D, and can be controlled within the surface decarburization 8 ‰ D, high demand decarbonization should be controlled within 0.05mm or 0.03mm.

Hardness and hardness uniformity:

When the metal material to be cold heading or cold extrusion, the need for a suitable hardness, in order to obtain a higher yield and lower mold losses. Of course, we also need to work with a lot of hard material
Uniformity (bulk hardness difference), which was within the range as small as possible; otherwise, fluctuated hardness, will seriously affect the efficiency of production, resulting in low yield, shortening the life of the mold.

Suitable hardness and hardness uniformity, depending on the temperature uniformity; and temperature uniformity, first of all depends ball furnace structure: lid, furnace, convection barrels, diversion seat, convection fan design optimization, able to meet the requirements of fluid dynamics; secondly, the choice of protective atmosphere, such as the use of highly active reducing gas to accelerate the heat conduction metal surface.

Hardness is usually scattered in poor control 3-5HRB able to meet production requirements, high demands should be controlled within the hardness difference scattered 3HRB.

After rolling steel, forged air cooling, the resulting organization is lamellar pearlite and reticular cementite, such organizations hard and brittle, not only difficult machining, and also easy to deformation and cracking after quenching process. And after the ball
Annealing globular pearlite structure is obtained, which takes the shape of spherical cementite particles dispersed in the ferrite matrix, and lamellar pearlite, compared not only low hardness, ease of machining, and the heating in quenching, Albright
Grain is not easy to grow, the cooling of the workpiece deformation and cracking tendency is small. So, when the molded parts having a large amount of deformation, the material needs to have a high level of ball rate and good microstructure. Otherwise,
Cause parts not easy to shape, pass rate and other issues.

The merits of ball rate and microstructure, and the ball furnace construction and related annealing process; construction aspect, a good atmosphere circulatory system, can be forced cooling apparatus control program, and a high efficiency can be controlled
Heating device heating rate; annealing process, the materials according to the material, material manufacturers, uses, etc., for the design, such as heating rate, cooling rate can be controlled.

Typically the rate of ball control in the 4.5-6 level (according to the Japanese JIS G3539 standard, six highest)

In addition to these technical indicators, the choice of ball annealing furnace, when we have the ball annealing furnace itself put forward some demands:

1, the sealing performance (48 hours of production can be maintained much pressure?)

In short, the ball annealing furnace construction quality and atmosphere control, automatic control, the annealing process design and other closely related; in actual production because of the above analysis is not produced individually, but will interact. Therefore, the choice of ball annealing furnace, you can refer to the above points, compared choose.